Due to the increasing demand for healthier food and beverages, the reduction of ethanol in alcoholic beverages, especially beer and wine, is of considerable commercial interest.
Low-alcohol, alcohol-free or reduced-alcohol beers (also called light beer, no-alcohol, non-alcoholic beer, small beer, small ale, near-beer) are beers with no alcohol or a low alcohol content which aim to reproduce the full flavor of standard beers which normally contain more than 4% (vol/vol) alcohol. In most of the EU countries beers with low alcohol content are divided into alcohol-free beers containing no more than 0.5% (vol/vol) alcohol, and into low-alcohol beers with no more than 1.2% (vol/vol) alcohol. In the United States alcohol-free beer means that there is no alcohol present, while the upper limit of 0.5% (vol/vol) alcohol corresponds to so-called non-alcoholic or near-beer (Montanari et al. 2009).
The conversion of wort into an alcoholic beer is the result of a fermentation process by Saccharomyces ssp. yeast resulting in the production of alcohol and fermentation-derived flavor compounds, such as esters (e.g. isoamyl acetate) and higher alcohols. Isoamyl acetate is a key flavor compound in beer (Saerens et al. 2010). The combination of the flavor of the raw materials, mostly malt and hops, together with the fermentation process, results in the unique flavor and taste of beers (Swiegers et al. 2007, Saerens et al. 2010).
Today beers with low alcohol contents are often made by producing full-strength beer (with an alcohol concentration of above 4% (vol/vol)) and then removing the alcohol by physical processes (boiling off the alcohol/distillation or reverse osmosis). In the case of some non-alcoholic or alcohol-free beers no fermentation takes place and in some cases the beers are produced by simply diluting full-strength beers with water.
As the physical processes result in the evaporation, loss or dilution of fermentation-derived flavor compounds (or a complete lack of fermentation-derived flavor compounds as in the case with unfermented non-alcoholic or alcohol-free beer), these types of beers are often characterized as being less flavorful than full-strength beer or may have an undesirable wort-like taste (Zufall and Wackerbauer. 2000).
German patent DD 288619 A5 describes the use of Pichia farinosa yeast strains to ferment unhopped beer wort to obtain an alcohol-free beverage with fruity aroma.
However, there exists a need for improved methods for preparing a low-alcohol or alcohol-free fermented beverage wherein the presence of desirable flavor compounds, such as esters and higher alcohols, is enhanced.